None.
Not applicable.
The invention is related to the field of power converters, and more particularly to multi-channel interleaved power converters.
Interleaved power converters employ two or more channels of conversion circuitry operating in a time-multiplexed or interleaved fashion. Although the control of interleaved converters is generally more complex than the control of non-interleaved converters, there are advantages that may offset the increased complexity in certain application. The advantages include, for example, reduced ripple and faster response to load transients.
One general aspect of interleaved converters is the degree of balance among the channels in sharing the load. It is generally desirable that the load be shared as equally as possible. Various techniques have been used to manage the sharing of the load among the different channels in interleaved converters. One general approach has been to sense the current in output inductors of the various channels, add these sensed values together and divide by the number of channels to obtain an average current, and then subtract the actual current in each channel from the average to obtain per-channel difference values. The difference value for each channel is then used to adjust the amount of current supplied by the channel so as to evenly distribute the current load among the channels. While this approach can be effective, the several steps involved in obtaining the per-channel difference values are arrived at in an indirect and somewhat inefficient fashion. It would be desirable to employ simpler load-sharing circuitry that provides per-channel current adjustment in a more direct manner.
In accordance with the present invention, a multi-channel interleaved power converter is disclosed having improved load-sharing circuitry.
The disclosed interleaved converter includes first and second per-channel conversion circuits, each including a pulse width modulator (PWM), a driver coupled to the PWM, an inductor coupled to the driver, and a current controlled current source (CCCS) coupled to sense the current in the inductor. The inductors of the per-channel circuits are coupled in common to an output node of the power converter. Load current provided by the different channels flows through the respective inductors.
The converter further includes current summing circuitry operative (i) to subtract the output current of the CCCS of the second channel from the output current of the CCCS of the first channel, (ii) to convert the difference current into a corresponding offset, and (iii) to apply the offset to a first PWM control signal to generate a second PWM control signal for the second per-channel circuit. The second PWM control signal is generated such that respective currents are established in the inductors of the different channels according to a predetermined desired current relationship. Commonly, the desired relationship is one of equality, i.e., equal sharing of load current, but other desired relationships are possible. In one embodiment, the current summing circuitry comprises a capacitor that integrates the difference between the two currents of the CCCSs to adjust the level of the second PWM control signal with respect to the first PWM control signal so as to bring about the desired current relationship in the inductors of the channels.
The disclosed converter achieves good balancing of load current among the different channels while economizing on circuit area and complexity, making it attractive from the perspectives of robustness and cost.
Other aspects, features, and advantages of the present invention will be apparent from the detailed description that follows.